Effect of spray conditions on the properties of HVOF Cr₃C₂-NiCr coatings

The effects of spray conditions on the properties of high velocity oxy-fuel (HVOF) Cr₃C₂-NiCr coatings are investigated using such parameters as oxygen flow, fuel gas flow and spray distance, based on the orthogonal regression experimental design method. Propane is used as the fuel gas. The properties of the coatings are characterized by adhesive strength, hardness, abrasive wear and erosion tests. The abrasive wear of the coatings is estimated using a dry-sand rubber wheel tester. The relationships between the properties of the coatings are examined. The results show clearly that the properties of the coatings are greatly influenced by oxygen and propane gas flows. Regression formulae are established for optimizing the spray conditions. There is no obvious relation between the hardness and wear resistance of HVOF Cr₃C₂-NiCr coatings. On the other hand, there are clear correlations between abrasive wear and erosion wear of the coatings.